All types of vehicles that we use, cars, motorcycles, trucks, ships,aeroplanes, and many other types work on the basis of second law ofthermodynamics and Carnot Cycle. They may be using petrol engine ordiesel engine, but the law remains the same.2)

All the refrigerators, deep freezers, industrial refrigeration systems, all typesof air-conditioning systems, heat pumps, etc work on the basis of thesecond law of thermodynamics.3)

All types of air and gas compressors, blowers, fans, run on variousthermodynamic cycles.4)

One of the important fields of thermodynamics is heat transfer, which relatesto transfer of heat between two media. The concept of heat transfer is usedin wide range of devices like heat exchangers, evaporators, condensers,radiators, coolers, heaters, etc.5)

Thermodynamics also involves study of various types of power plants likethermal power plants, nuclear power plants, hydroelectric power plants,power plants based on renewable energy sources like solar, wind,geothermal, tides, water waves etc,6)

Renewable energy is an important subject area of thermodynamics thatinvolves studying the feasibility of using different types of renewable energysources for domestic and commercial use.

Fuel + AirBurn to produceHEATHeat enginee.g. Car engine(or power plant)Movement of carorElectrical energyWORKApplications of thiscourseExampleProducts of combustionExhaustHeat transfer tocooling water oratmospheric air

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1.1 Thermodynamics and EnergyDefinitionSciencethat deals withheat and workand the changes they can produce.e.g. change of temperature (T), pressure (P) etc.Basis is experimental observations written down as laws. e.g.1stlaw of thermodynamics:

Energy can change from one form to another but the total amount remainsconstant.2ndlaw of thermodynamics:

Energy hasquality(more or less useful) and quantity. Real changes occur onlyin a direction of decreasing quality of energy.Microscopic and Macroscopic Approach

To study the behavior (changes inT&P) of substances we have 2 approachesMicroscopic:Study behavior of each atom & molecule (Quantum mechanics)Macroscopic:Study average behavior of many atom & moleculea) Find the average behavior based on probability theory (Statisticalthermodynamics)b) Find the average behavior using instruments

ClassicalThermodynamicsWe study the average behavior of many atoms/molecules using instruments.e.g. average pressure (using a pressure measuring device)average temperature (using a thermometer).

1.2 Dimensions and Units

1.2 Dimensions and Units (contd.)Dimensions and Units

Thermodynamic SystemA quantity of matter or a region in space chosen for study.SurroundingsEverything external to the system.BoundarySurface that separates the system from the surrounding. It may befixedormovable1-3 Systems and Control Volume



Closed system (Control mass)A fixed amount of mass chosen for study (nomass can cross its boundary). Heat andwork can cross the boundary, volume mayalso change.e.g. piston cylinder.Open system (Control volume)A selected region chosen for study. Mass,heat and work can cross its boundary,volume may also change.e.g. water heater, car radiator, turbine,nozzle.Isolated systemA system closed to mass, heat and workflows. It is not affected by the surroundings.1-3 Closed and Open Systems

A substance can be at variouspressures & temperatures or invariousstatesStateCondition of a system identified by properties (e.g.T, P, v).In a given state each property has 1 value.Properties are defined when the system is inEquilibriumNo unbalance exist in the system,and values of properties (T, P etc.) remain thesame when it is isolated from the surroundings.Thermal equilibrium:temperature of system does not change when it is isolated fromsurroundingsMechanical equilibrium:pressure of system does not change when it is isolated fromsurroundings

Chemical equilibrium:chemical composition does not change when it is isolated fromsurroundings

18

The state postulate

The state of a simple compressible system iscompletely specified by2independentintensive

properties

1.7 Processes and Cycles

Process

The transformation of a system from one state to another state through asuccession of states

The state of a system is defined when it is in equilibrium.If we change the state very fast it is not in equilibrium during the process(non-equilibriumprocess)If we change it slowly then the system is in equilibrium during the process(quasi-equilibriumprocess)Quasi-equilibrium process (ideal process)The system is very near to equilibrium in all successive states during the process.Non-equilibrium processThe system is not in equilibrium during the process. States during the process areundefinedWe can only define the initial and final states.

Properties like pressure (P) and volume (V) can be plotted during a process

1.7 Processes and Cycles -The steady flow processDefined for open systems (Control volume) for which conditions do notchange with time at each location during the process.

1.7 Forms of Energy

Energy contained in a system is also a property since it tells us the condition of the systemEnergy may be contained (stored) in a system asMicroscopic formEnergy related to molecular structurecalledInternal energydenoted byUMacroscopic formEnergy related to motion or elevationof the system e.g.KE =!mV2orPE = mgz

1.7 Forms of Energy

Energy is contained in a system asinternal, kinetic and potentialenergyEnergy transfers at the system boundary asheat and work

Forms of EnergyThe portion of the internal energy of a systemassociated with the1.

kinetic energies of the molecules is called thesensible energy.2.

phase of a system is called thelatent energy.3.

atomic bonds in a molecule is calledchemicalenergy.4.

strong bonds within the nucleus of the atom itselfis callednuclear energy.5.

Transfers (enters or leaves)at the system boundary asHeat or WorkEnergy is contained in a system (as U + KE + PE) and can be transferred at the systemboundary (as Heat or Work)3 ways in which energy is stored as internal energy (U) –microscopic form- ineach phase of a substance.1.

Intermolecular potential energy2.

Molecular kinetic energy3.

Intra molecular energy1.7 Forms of Energy



3 ways in which energy is stored as internal energy (U)

Intermolecular potential energyBecause of forces between molecules.At low densities particles are far away intermolecular PE is low then we call it GASIf it is assumed to be zero, so we have independent molecules, we call it IDEAL GASMolecular kinetic energyBecause of translational motion of moleculesIt depends on the mass and velocities of the moleculesIntra molecular energy

(within individual molecules)Because of the molecular and atomic structure and related forcesVery small compared with the other forms.1.7 Forms of Energy

Latent energyEnergy related to binding forces. Strongest in solids, weakest in gases.If sufficient energy is added to the molecules of a solid or liquid they break away and thesubstance becomes vapor. This is phase change process and the related energy is calledlatent energy

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1.8 Temperature and 0thlaw of thermodynamicsTemperature:Degree of hotness of coldness

0thlaw of thermodynamicsWhen 2 bodies have equality of temperature with a 3rd body, then they haveequality of temperature with each other.TA

TB

TC

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1.8 Temperature and 0thlaw of thermodynamicsTemperature Scales:To relate temperatures that we read fromdifferent devices we need a standard scale of temperatureIce point (0oC)

The temperature of a mixture of ice and water in equilibriumat a pressure of 1 atmosphere.Steam point (100oC)The temperature of water and steam which are inequilibrium at a pressure of 1 atmosphere.Triple point of water (0.01oC)A single fixed point at a state in which the solid, liquid andvapor phases of water all exist in equilibrium.Absolute scale of temperature:A temperature scale independent of any thermometricsubstance

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In thermodynamics we useabsolute pressure(P)devices or instruments measuregauge pressure(Pg)which is the pressure above or below theatmospheric pressure(PatmorP0)1.9 Pressure

1.10 PressurePoints 1 and 2 at the same heightand connected by the same liquidhave the same pressure. i.e.

PPatm

Barometer:used to measure absolutepressure

Manometer:used to measure gauge pressure

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Piston and Cylinder1.10 PressureAt equilibriumFext= P.AP

If the system is heated thefree moving

piston will move to adjust the insidepressure so thatFext= P.APExternal forcesFext